Thanks for posting to the Community, @jamesvanoudtshoo.
You can edit the bank account info for you to disconnect the linked bank account.
Let me show you how:
- Go to Banking on the left pane and then select Banking.
- Choose the bank account and click the Pencil icon.
- Select Edit account info.
- Check Disconnect this account on save box.
- Click Save and Close.
For more details and information about deleting bank and other types of accounts, you can check this article: Delete an account on your chart of accounts in QuickBooks Online.
Please keep me notified by leaving a message through this post if you need further assistance. I'm always here to help. Enjoy your day!